The domestication of many plants has correlated with dramatic increases in yield. Most phenotypic variation occurring in natural populations is continuous and is effected by multiple gene influences. The identification of specific genes responsible for the dramatic differences in yield, in domesticated plants, has become an important focus of agricultural research.
In Arabidopsis, the ERECTA gene has been shown to control organ growth and flower development by promoting cell proliferation (Shpak, et al., (2003) Plant Cell 15:1095-1110; Development (2004) 131:1491-501). The Arabidopsis ERECTA gene affects inflorescence development, and controls organ growth by promoting cell proliferation. Transgenic Arabidopsis plants that ectopically over express the ERECTA gene improve plant transpiration efficiency and drought tolerance by affecting stomatal density, epidermal cell expansion, mesophyll cell proliferation and cell-cell contact. The ERECTA gene encodes a leucine-rich repeat receptor-like kinase (LRR-RLK) and may controlling plant growth/organ size and biomass accumulation. In addition, Masle Gilmore and Farquhar, Nature (2005) 436:866, indicates that the Arabidopsis ERECTA gene is responsible for plant transformation efficiency, in addition to the varied effects it is already known to have on plant architecture. There are implications for agriculture, especially in the area of drought tolerance and agronomic performance.
ERECTA is associated with growth enhancement. The ERECTA genes may find utility in controlling the size of the whole plants, or specific organs in maize or other crops. Potential usage of this gene are over expressing it in transgenics to increase biomass accumulation, targeting the gene expression to specific tissues using tissue-specific promoters for enhanced root growth, accelerated seedling growth for fast canopy closure, larger leaf, increased ear size, enhanced embryo, endosperm growth for larger kernel and manipulate the content of oil, protein or starch in the whole kernel, and etc. By altering the silk growth rate one could manipulate the synchronization or ASI (anthesis and silking interval), which may improve stress tolerance. Another potential application is in improving the transformation and regeneration of crop plants from in vitro tissue culture. One could control the expression of this gene to increase cell proliferation rate and cultured tissue growth rate. ERECTA could also be used to manipulate the gene to reduce the organ size such as tassel size by down regulation of the expression in specific tissues. The ERECTA genes can be useful for enhancing drought tolerance by improving the transpiration efficiency in maize and other crops. Exploring natural allelic variation of this gene can be used in breeding improvement or transgenics by identifying allele haplotypes that are associated with the stress tolerant phenotypes of inbreds. The gene maps to a chromosomal location in the general vicinity of drought QTLs, suggesting possibly tolerant allele variants.
The present invention includes the identification of the putative maize ERECTA genes, ZmERECTA A and B (SEQ ID NOS: 5 and 7) that are related to the Arabidopsis ERECTA genes (SEQ ID NOS: 1 and 3). The ortholog having the most similarity to Arabidopsis ERECTA (SEQ ID NO: 1), is ZmERECTA 1 (SEQ ID NO: 5). The expression is associated with immature reproductive tissues, and is found mainly in the inflorescence meristem and shoot apical meristem and to a lesser degree in other meristem related tissues.
Transgenic plants expressing ZmERECTA A (SEQ ID NO: 5) are expected to show a positive impact on biomass accumulation and rate of maize plant growth, as well as an increase in organ size. Transgenic plants expressing ZmERECTA are also expected to show improved drought tolerance. These maize genes will find utility for enhancing agronomic traits in maize (and other crops).
The present invention also includes the identification of ERECTA genes in other plant species. The rice gene family is represented by 2 family members. Four gene sequences were also found in Soybean (Glycine max) and 3 genes in Sorghum bicolor. Two members of the ERECTA Arabidopsis gene family are disclosed herein.